Process for preparing polycarbamate and reaction product thereof

ABSTRACT

A first process to produce polycarbamate comprising providing urea in liquid form; and adding the liquid urea to a polyol is provided. A second process for producing polycarbamate comprising adding solid urea to a polyol in liquid form to form a reaction mixture is provided. Also provided is a reaction product produced by the first process or second process.

FIELD OF INVENTION

The instant invention relates to a process for preparing polycarbamateand a reaction product thereof.

BACKGROUND OF THE INVENTION

Polyurethane is a polymer composed of a chain of organic units withcarbamate linkages. Polyurethanes may be produced using isocyanate as astarting material. However, trace amounts of residual isocyanates raisehealth and safety concerns. As an alternative, polyurethanes have beenproduced using polyols and methyl carbamate as the starting materials.Methyl carbamate, however, also gives rise to health and safetyconcerns. There remains a need for alternative polyurethane productionmethods which provide polyurethanes useful in a variety of applicationswhile minimizing health and safety concerns.

SUMMARY OF THE INVENTION

The instant invention is a process for preparing a polycarbamate and areaction product thereof.

In one embodiment, the instant invention provides a first process toproduce polycarbamate comprising: providing urea in liquid form; andadding the liquid urea to a polyol. In an alternative embodiment, theinstant invention provides a second process to produce polycarbamatecomprising: adding solid urea to a polyol in liquid form to form areaction mixture.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention is a process for preparing a polycarbamate and areaction product thereof.

First Process

The first process according to the present invention comprises providingurea in liquid form; and adding the liquid urea to a polyol.

Urea

The liquid form of the urea (or “liquid urea”) may be achieved in anyacceptable manner. For example, the urea may be dissolved in a firstsolvent. Alternatively, the urea may be melted. In yet anotheralternative, the urea may be suspended in a clathrate. A urea clathratemay also be known as a urea inclusion compound and may have thestructure as described in “Supramolecular Chemistry” John Wiley & Sons,Jonathan w. Steed, Jerry L. Atwood, pp. 393-398 and Harris, K. D. M.,“Fundamental and Applied Aspects of Urea and Thiourea InclusionCompounds”, Supramol. Chem. 2007, 19, 47-53.

The liquid form of the urea may alternatively be present in acombination of liquid forms.

In a particular embodiment, the urea is dissolved in water. In anotherembodiment, the urea may be dissolved in a mixture of two or more firstsolvents. Such first solvents include organic solvents. In analternative embodiment, the urea is dissolved in one or more firstsolvents selected from water and organic alcohols. In one embodiment,urea is partially soluble in the first solvent or mixture of firstsolvents. In yet another embodiment, urea is fully soluble in the firstsolvent or mixture of first solvents.

Polyol

As used herein, the term “polyol” means an organic molecule having atleast 2-OH functionalities. As used herein, the term “polyester polyol”means a subclass of polyol that is an organic molecule having at least 2alcohol (—OH) groups and at least one carboxylic ester (CO₂—C)functionality. The term “alkyd” means a subclass of polyester polyolthat is a fatty acid-modified polyester polyol wherein at least onecarboxylic ester functionality is preferably derived from anesterification reaction between an alcoholic —OH of the polyol and acarboxyl of a (C₈-C₆₀) fatty acid. The polyol may be any polyol; forexample, the polyol may be selected from the group consisting ofacrylic, styrene-acrylic, styrene-butadiene, saturated polyester,polyalkylene polyols, urethane, alkyd, polyether or polycarbonate. Inone exemplary embodiment, the polyol component comprises hydroxyethylacrylate. In another exemplary embodiment, the polyol componentcomprises hydroxyethyl methacrylate.

The reaction mixture may comprise from 10 to 100 percent by weight ofpolyol; for example, from 30 to 70 percent by weight of polyol. In oneembodiment, the polyol has a functional structure of a 1,2-diol,1,3-diol, or combinations thereof.

The polyol can be non-cyclic, straight or branched; cyclic andnonaromatic; cyclic and aromatic, or a combination thereof. In someembodiments the polyol comprises one or more non-cyclic, straight orbranched polyols. For example, the polyol may consist essentially of oneor more non-cyclic, straight or branched polyols.

In one embodiment, the polyol consists essentially of carbon, hydrogen,and oxygen atoms. In another embodiment, the polyol consists of primaryhydroxyl groups. In yet another embodiment, the hydroxyl groups are inthe 1,2 and/or 1,3 configuration. Exemplary polyol structures are shownbelow for illustrative purposes.

Polyol useful in embodiments of the inventive process include oligomersor polymers derived from hydroxy-containing acrylic monomeric units.Suitable monomers may be, but are not limited to, hydroxyethyl acrylate,hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxydodecyl acrylate,hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutylmethacrylate, hydroxydodecyl methacrylate, hydroxybutyl vinyl ether,diethylene glycol vinyl ether and a combinations thereof. The polyoluseful in embodiments may be prepared by reacting at least onehydroxyl-containing monomer with one or more monomers. Suitable monomersmay be, but are not limited to, vinyl monomers such as styrene, vinylether, such as ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinylether, ester of unsaturated carbonic acid and dicarbonic acid, such asmethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, dodecylacrylate, dodecyl methacrylate, dimethyl maleate and a mixture thereof.

Polyols useful in certain embodiments of the inventive process includepolyether polyols and polyester polyols. Suitable polyols include, forexample, ethylene glycol, diethylene glycol, neopentyl glycol,1,4-butanediol, 1,6-hexanediol, glycerol, pentaerythritol, sorbitol andmannitol. Suitable glycols thus include ethylene glycol, propyleneglycol, diethylene glycol, triethylene glycol, tetraethylene glycol,pentaethylene glycol, hexaethylene glycol, heptaethylene glycol,octaethylene glycol, nonaethylene glycol, decaethylene glycol, neopentylglycol, glycerol, 1,3-propanediol, 2,4-dimethyl-2-ethyl-hexane-1,3-diol,2,2-dimethyl-1,2-propanediol, 2-ethyl-2-butyl-1,3-propanediol,2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 2,2,4-tetramethyl-1,6-hexanediol,thiodiethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol,2,2,4-tetramethyl-1,3-cyclobutanediol, p-xylenediol, hydroxypivalylhydroxypivalate, 1,10-decanediol, hydrogenated bisphenol A,trimethylolpropane, trimethylolethane, pentaerythritol, erythritol,threitol, dipentaerythritol, sorbitol, mannitol, glycerine,dimethylolpropionic acid, and the like.

Polycarboxylic acids useful in the invention may include, but are notlimited to, phthalic anhydride or acid, maleic anhydride or acid,fumaric acid, isophthalic acid, succinic anhydride or acid, adipic acid,azeleic acid, and sebacic acid, terephthalic acid, tetrachlorophthalicanhydride, tetrahydrophthalic anhydride, dodecanedioic acid, sebacicacid, azelaic acid, 1,4-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,glutaric acid, trimellitic anhydride or acid, citric acid, pyromelliticdianhydride or acid, trimesic acid, sodium sulfoisophthalic acid, aswell as from anhydrides of such acids, and esters thereof, where theyexist. Optionally monocarboxylic acids may be employed including, butnot limited to, benzoic acid. The reaction mixture for producing alkydsincludes one or more aliphatic or aromatic polycarboxylic acids,esterified polymerization products thereof, and combinations thereof. Asused herein, the term “polycarboxylic acid” includes both polycarboxylicacids and anhydrides thereof. Examples of suitable polycarboxylic acidsfor use in the present invention include phthalic acid, isophthalicacid, terephthalic acid, tetrahydrophthalic acid, naphthalenedicarboxylic acid, and anhydrides and combinations thereof.

Addition Step

In a certain embodiment of the first process, the adding the urea inliquid form to the polyol is conducted in the presence of a catalyst.Suitable catalysts for use in this process include, but are not limitedto, organo-tin compounds. The use of this type of catalyst is well knownin the art. Examples of catalysts useful in the present inventioninclude, but are not limited to, dibutyltin diacetate, and dibutyltinoxide. In a particular embodiment, the catalyst is used in an amountfrom 0.1% to 1.0 wt % based on polyol weight. All individual values andsubranges from 0.1 to 1.0 wt % are included herein and disclosed herein;for example, the catalyst amount may range from a lower limit of 0.1,0.2, 0.4, 0.6 or 0.8 wt % based on polyol weight to an upper limit of0.15, 0.3, 0.5, 0.7, 0.9 or 1.0 wt % based on polyol weight. Forexample, the catalyst amount, in certain embodiments, may be from 0.1 to1.0 wt % based on polyol weight, or in the alternative, from 0.5 to 1.0wt % based on polyol weight, or in the alternative, from 0.1 to 0.6 wt %based on polyol weight.

The adding the urea in liquid form to polyol may be accomplished by anymeans. In a particular embodiment of the first process, the adding theurea in liquid form to the polyol is conducted in a batch manner. In aparticular embodiment of the first process, the adding the urea inliquid form to the polyol is conducted in a semi-batch manner. In oneembodiment, the urea in liquid form is added at a constant rate over aperiod of time in which the reaction proceeds. In yet anotherembodiment, the urea in liquid form is added to the polyol at more thanone rate, with the rate changing over the time period in which thereaction proceeds. In yet another embodiment, the urea in liquid form isadded to the polyol using a pulsed constant rate in which the urea isadded at a rate for a first period of time, followed by a second periodof no urea addition, followed by urea addition at the same rate for athird period of time, and so on. In another alternative embodiment, theurea in liquid form is added to the polyol using a pulsed variable ratein which the urea is added at a first rate for a first period of time,followed by a second period of no urea addition, followed by ureaaddition at a second rate for a third period of time, and so on.

In one embodiment of the first process, the polyol is complete polyol inthe absence of any solvent. In an alternative embodiment of the firstprocess, the polyol is dissolved in a second solvent prior to the addingthe liquid urea to the dissolved polyol. The second solvent may be anysolvent or mixture of solvents in which the polyol is soluble orpartially soluble. In certain embodiments, the first and second solventsform a heterogeneous azeotrope allowing removal of the first solvent bydecantation or other means. In certain embodiments, removal of the firstsolvent from a heterogenous azeotrope permits concurrent removal ofcertain by-products, such as ammonia, which are soluble in the firstsolvent. In yet an alternative embodiment, the first and second solventsform a heterogeneous azeotrope allowing removal of the first solvent andfurther wherein the second solvent is returned to the reactor.

In certain embodiments, the first process achieves at least a 50%conversion of hydroxyl groups of the polyol. All individual values andsubranges from at least 50% conversion are included herein and disclosedherein; for example, the hydroxyl conversion may range from a lowerlimit of 50%, or in the alternative, the hydroxyl conversion may rangefrom a lower limit of 55%, or in the alternative, the hydroxylconversion may range from a lower limit of 60%, or in the alternative,the hydroxyl conversion may range from a lower limit of 65%, or in thealternative, the hydroxyl conversion may range from a lower limit of70%, or in the alternative, the hydroxyl conversion may range from alower limit of 75% or in the alternative, the hydroxyl conversion mayrange from a lower limit of 80%, or in the alternative, the hydroxylconversion may range from a lower limit of 85%.

Reaction Product of First Process

In another alternative embodiment, the instant invention provides areaction product of any of the embodiments of the first processdisclosed herein.

In one embodiment, the reaction product of the first process exhibits aGardner color of less than or equal to 2. All individual values andsubranges are included herein and disclosed herein; for example, theGardner color index may be from an upper limit of 2 or 1.

In one embodiment, the reaction product of the second process exhibits aGardner color of less than or equal to 2. All individual values andsubranges are included herein and disclosed herein; for example, theGardner color index may be from an upper limit of 2 or 1.

In specific embodiments, a 100% solids reaction product of the firstprocess comprises less than 0.2 wt % cyanuric acid. All individualvalues and subranges from less than 0.2 wt % are included herein anddisclosed herein. For example, the amount of cyanuric acid may be lessthan 0.2 wt %, or in the alternative, less than 0.1 wt %, or in thealternative, less than 0.09 wt %, or in the alternative, less than 0.07wt %, or in the alternative, less than 0.04 wt %, or in the alternative,less than 0.02 wt %. In a particular embodiment, the amount of cyanuricacid present in a 100% solids reaction product is from 0.05 to 0.15 wt%, or in the alternative, from 0.1 to 0.2 wt %.

In specific embodiments, a 100% solids reaction product of the firstprocess comprises less than 0.6 wt % biuret. All individual values andsubranges from less than 0.6 wt % are included herein and disclosedherein. For example, the amount of biuret may be less than 0.6 wt %, orin the alternative, less than 0.55 wt %, or in the alternative, lessthan 0.52 wt %, or in the alternative, less than 0.4 wt %, or in thealternative, less than 0.36 wt %, or in the alternative, less than 0.1wt %. In a particular embodiment, the amount of biuret present in a 100%solids reaction product of the first process is from 0.35 to 0.6 wt %,or in the alternative, from 0.4 to 0.6 wt %, or in the alternative, from0.01 to 0.1 wt %.

In specific embodiments, a 100% solids reaction product of the firstprocess comprises less than 2 wt % polyallophanate. All individualvalues and subranges from less than 2 wt % are included herein anddisclosed herein. For example, the amount of polyallophanate present ina 100% solids reaction product is less than 2 wt %, or in thealternative, less than 1.8 wt %, or in the alternative, less than 1.0 wt%, or in the alternative, less than 0.6 wt %, or in the alternative,less than 0.3 wt %, or in the alternative, less than 0.1 wt %. In aparticular embodiment, the amount of polyallophanate present in a 100%solids reaction product of the first process is from 0.3 to 2 wt %, orin the alternative, from 0.55 to 0.15 wt %, or in the alternative, from0.01 to 0.05 wt %.

Second Process

In an alternative embodiment, the instant invention further provides asecond process for producing polycarbamate comprising adding solid ureato a polyol in liquid form to form a reaction mixture.

Polyols suitable for use in the second process are identical to thosediscussed in connection with the first process. The liquid form of thepolyol may arise from any means, such as, by dissolution in a solvent, anon-dissolved yet liquid polyol or by melting.

In one specific embodiment, the temperature of the reaction mixture isabove the melting point of urea.

In one embodiment of the second process, the adding the solid urea isconducted in a batch manner. In yet another embodiment of the secondprocess, the adding the solid urea to the polyol is conducted in asemi-batch manner. In one embodiment, the urea is added at a constantrate over a period of time in which the reaction proceeds. In yetanother embodiment, the urea is added to the polyol at more than onerate, with the rate changing over the time period in which the reactionproceeds. In yet another embodiment, the urea is added to the polyolusing a pulsed constant rate in which the urea is added at a rate for afirst period of time, followed by a second period of no urea addition,followed by urea addition at the same rate for a third period of time,and so on. In another alternative embodiment, the urea is added to thepolyol using a pulsed variable rate in which the urea is added at afirst rate for a first period of time, followed by a second period of nourea addition, followed by urea addition at a second rate for a thirdperiod of time, and so on.

In a certain embodiment of the second process, the adding the urea tothe polyol is conducted in the presence of a catalyst. Suitablecatalysts for use in this process include, but are not limited to,organo-tin compounds. The use of this type of catalyst is well known inthe art. Examples of catalysts useful in the present invention include,but are not limited to, dibutyltin diacetate, and dibutyltin oxide. In aparticular embodiment, the catalyst is used in an amount from 0.1% to1.0 wt % based on polyol weight. All individual values and subrangesfrom 0.1 to 1.0 wt % are included herein and disclosed herein; forexample, the catalyst amount may range from a lower limit of 0.1, 0.2,0.4, 0.6 or 0.8 wt % to an upper limit of 0.15, 0.3, 0.5, 0.7, 0.9 or1.0 wt %. For example, the catalyst amount, in certain embodiments, maybe from 0.1 to 1.0 wt %, or in the alternative, from 0.5 to 1.0 wt %, orin the alternative, from 0.1 to 0.6 wt %.

In another alternative embodiment, the instant invention provides areaction product of any of the embodiments of the second processdisclosed herein.

In one embodiment, the reaction product of the second process exhibits aGardner color of less than or equal to 2. All individual values andsubranges are included herein and disclosed herein; for example, theGardner color index may be from an upper limit of 2 or 1.

In specific embodiments, a 100% solids reaction product of the secondprocess comprises less than 0.2 wt % cyanuric acid. All individualvalues and subranges from less than 0.2 wt % are included herein anddisclosed herein. For example, the amount of cyanuric acid present inthe 100% solids reaction product is less than 0.2 wt %, or in thealternative, less than 0.1 wt %, or in the alternative, less than 0.09wt %, or in the alternative, less than 0.07 wt %, or in the alternative,less than 0.04 wt %, or in the alternative, less than 0.02 wt %. In aparticular embodiment, the amount of cyanuric acid present in the 100%solids reaction product is from 0.01 to 0.2 wt %, or in the alternative,from 0.1 to 0.2 wt %.

In specific embodiments, a 100% solids reaction product of the secondprocess comprises less than 0.6 wt % biuret. All individual values andsubranges from less than 0.6 wt % are included herein and disclosedherein. For example, the amount of biuret present in the 100% solidsreaction product is less than 0.6 wt %, or in the alternative, less than0.55 wt %, or in the alternative, less than 0.52 wt %, or in thealternative, less than 0.4 wt %, or in the alternative, less than 0.36wt %. In a particular embodiment, the amount of biuret present in the100% solids reaction product of the second process is from 0.35 to 0.4wt %, or in the alternative, from 0.35 to 0.38 wt %.

In specific embodiments, a 100% solids reaction product of the secondprocess comprises less than 2 wt % polyallophanate. All individualvalues and subranges from less than 2 wt % are included herein anddisclosed herein. For example, the amount of polyallophanate present inthe 100% solids reaction product is less than 2 wt %, or in thealternative, less than 1.8 wt %, or in the alternative, less than 1.0 wt%, or in the alternative, less than 0.6 wt %, or in the alternative,less than 0.3 wt %. In a particular embodiment, the amount ofpolyallophanate present in the 100% solids reaction product of thesecond process is from 0.25 to 1.2 wt %, or in the alternative, from0.26 to 0.75 wt %.

EXAMPLES

The following examples illustrate the present invention but are notintended to limit the scope of the invention.

Example 1 Batch Process to Produce Polycarbamate from Reaction of Ureaand Polyol

A 1-L reactor with heating mantle was used in the reaction. The reactorwas equipped with an agitator, a thermal-couple and a nitrogen sparger.A water-cooled condenser was connected to the adaptor on the reactorlid. The overhead condensate was collected by a receiver and thenon-condensable went through a bubbler filled with mineral oil and thenentered a 1-L scrubber filled with water.

850 g PARALOID™ AU-608X polyol which consists of 58% solid and 42%solvent (xylenes) was added to the reactor. PARALOID AU-608X is anacrylic polyol which is commercially available from The Dow ChemicalCompany. The polyol used in Inventive Example 1 has 0.76 mol hydroxylfunctionality. 5.20 g dibutyltin oxide (98% pure) was added to thereactor. 45.87 g 99% pure urea was used in this reaction. The heatingmantle was started and set at 158° C. The nitrogen sparging flow ratewas set at 20 sccm. The reaction mixture was agitated at 100 rpm andthen adjusted to 400 rpm when the reactor temperature was over 60° C.Urea was added to the reactor when the reactor temperature was over 130°C. The reaction was carried out at 138-142° C. for 12 hours. After thereaction was complete, the heating mantle was shut down and theagitation rate was reduced to 60 rpm. When the reactor temperaturedropped to 60° C., the polycarbamate product was poured out from thereactor. The final product was analyzed using ¹³C NMR. 800.6 gpolycarbamate with hydroxyl conversion of 82.3% was obtained. Thestarting polyol was clear and colorless. The polycarbamate product had aGardner color of 3 and further contained solid particles. By microscopicexamination, the solid particles were amorphous in shape and had a sizeranging from 5 to 60 μm across the largest dimension. By-productconcentration was measured based upon the 100% solids product weight.Table 1 provides the results of by product testing.

TABLE 1 Biuret Biuret + Cyanuric (wt % in Cyanuric Acid Polyallophanateacid + 100% solids (wt % in 100% (wt % in p100% polyallophate (wt % inproduct) solids product) solids product) 100% solids product) 0.47%0.10% 1.70% 2.27%

Example 2 Semi-Batch Process to Produce Polycarbamate from Solid Ureaand Polyol

A 1-L reactor with heating mantle was used in this reaction. The reactorhad a glass agitator at the center neck on the lid and a nitrogensparger to the bottom of the reactor. The reactor temperature wasmeasured using a thermal couple. A water-cooled condenser was connectedto the adaptor on the reactor lid. The overhead condensate was collectedby a receiver and the non-condensable went through a bubbler filled withmineral oil and then entered a 1-L scrubber filled with water.

929.35 g polyol PARALOID™ AU-608X which consists of 58% solid and 42%solvent (xylenes) was added to the reactor, which had 0.83 mol hydroxylfunctionality. 5.69 g dibutyltin oxide (98% pure) was added to thereactor. 52.9 g 99% pure urea was used for this reaction. The heatingmantle was started and set at 158° C. The nitrogen sparging flow ratewas set at 20 sccm. The reaction mixture was agitated at 100 rpm andthen adjusted to 400 rpm when the reactor temperature was over 60° C.

Urea was added to the reactor using a semi-batch method. When thereactor temperature was over 130° C., 60% of the total urea (31.7 g) wasadded to the reactor. The reaction was carried out at 138-142° C. Therest 40% of total urea (21.2 g) was added into the reactor in 4 equalportions (10% of the total urea each portion, 5.02 g) at 5 hrs, 9.5 hrs,13.5 hrs and 16.5 hrs. The total reaction time was 20 hours. After thereaction was complete, the heating mantle was shut down and theagitation rate was reduced to 60 rpm. When the reactor temperaturedropped to 60° C., the polycarbamate product was poured out from thereactor. The final product was analyzed using ¹³C NMR. 915.0 gpolycarbamate with hydroxyl conversion of 85.6% was obtained.

The starting polyol was clear and colorless. The polycarbamate producthad a Gardner color of 2 and no solid particles were detected visuallyor by microscopic examination. By-product concentrations were measuredbased upon the 100% solids polycarbamate product weight. Table 2provides the results of by product testing.

TABLE 2 Biuret Biuret + Cyanuric (wt % in Cyanuric Acid Polyallophanateacid + 100% solids (wt % in 100% (wt % in 100% polyallophate (wt % inproduct) solids product) solids product) 100% solids product) 0.35%0.01% 0.26% 0.62%

Example 3 Semi-Batch Process to Produce Polycarbamate from Aqueous UreaSolution and Polyol

A 1-L reactor with heating mantle was used in this reaction. The reactorhad a glass agitator at the center neck on the lid and a nitrogensparger to the bottom of the reactor. The reactor temperature wasmeasured using a thermal couple. A water-cooled condenser was connectedto the adaptor on the reactor lid. The overhead condensate was collectedby a receiver and the non-condensable went through a bubbler filled withmineral oil and then entered a 1-L scrubber filled with water. A syringepump with accurate feeding rate was used for urea aqueous solutionfeeding. Another syringe pump was used for solvent recycling.

800.1 g polyol PARALOID′ AU-608X which consists of 58% solid and 42%solvent (xylenes) was added to the reactor, which had 0.71 mol hydroxylfunctionality. 4.90 g dibutyltin oxide (98% pure) was added to thereactor. 100.0 g xylenes was added to the reactor to keep a lowviscosity for the reaction. The heating mantle was started and set at158° C. The nitrogen sparging flow rate was set at 20 sccm. The reactionmixture was agitated at 100 rpm and then adjusted to 400 rpm when thereactor temperature was over 60° C.

43.17 g 99% pure urea was dissolved in 40.0 g deionized water to form aurea aqueous solution. The solution was charged into a syringe. When thereactor temperature reached 140° C., the syringe pump was started at 2ml/min for a period of 10 minutes 51 seconds, during which 30% of totalurea solution (21.7 ml) was fed into the reactor. The pump feeding wasstopped. When the reaction time reached 3 hrs 10 minutes, the pumpfeeding was started at 40 ml/hr for approximate 38 minutes to add 35%urea solution (25.3 ml) to the reactor. The pump was then stopped. Whenthe reaction time reached 8 hrs, the pump feeding was started at 5 ml/hrfor the rest 35% urea solution (25.3 ml). At reaction time of 13 hrs,urea solution feed was complete. During urea aqueous solution feeding,an azeotrope of water and xylenes was collected in the overheadreceiver. The overhead liquid was collected and separated every hourfrom the receiver. The xylenes phase was rinsed with equal mass ofdeionized water and pumped back to the reactor.

The total reaction time was 17 hours. After the reaction was complete,the heating mantle was shut down and the agitation rate was reduced to60 rpm. When the reactor temperature dropped to 60° C., thepolycarbamate product was poured out from the reactor. The final productwas analyzed using ¹³C NMR. 804 g polycarbamate with hydroxyl conversionof 80.4% was obtained.

The starting polyol was clear and colorless. The polycarbamate producthad a Gardner color of less than or equal to 1 and no solid particleswere detected visually or by microscopic examination. By-productconcentrations were measured based upon the 100% solids polycarbamateproduct weight. Table 3 provides the results of by product testing.

TABLE 3 Biuret Biuret + Cyanuric (wt % in Cyanuric Acid Polyallophanateacid + 100% solids (wt % in 100% (wt % in 100% polyallophate (wt % inproduct) solid product) solids product) 100% solids product) 0.05% 0.01%0.03% 0.09%

Test Methods

Test methods include the following:

OH Number Titration

Where OH number is the magnitude of the hydroxyl number for a polyol asexpressed in terms of milligrams potassium hydroxide per gram of polyol(mg KOH/g polyol). Hydroxyl number (OH #) indicates the concentration ofhydroxyl moieties in a composition of polymers, particularly polyols.The hydroxyl number for a sample of polymers is determined by firsttitrating for the acid groups to obtain an acid number (mg KOH/g polyol)and secondly, acetylation with pyridine and acetic anhydride in whichthe result is obtained as a difference between two titrations withpotassium hydroxide solution, one titration with a blank for referenceand one titration with the sample. A hydroxyl number is the weight ofpotassium hydroxide in milligrams that will neutralize the aceticanhydride capable of combining by acetylation with one gram of a polyolplus the acid number from the acid titration in terms of the weight ofpotassium hydroxide in milligrams that will neutralize the acid groupsin the polyol. A higher hydroxyl number indicates a higher concentrationof hydroxyl moieties within a composition. A description of how todetermine a hydroxyl number for a composition is well-known in the art,for example in Woods, G., The ICI Polyurethanes Book, 2^(nd) ed. (ICIPolyurethanes, Netherlands, 1990).

Gardner Color:

was measured according to ASTM D1544 “Standard Test Method for Color ofTransparent Liquids (Gardner Color Scale)” using a HunterLabcolorimeter.

¹³C NMR:

All samples were characterized by ¹³C NMR in solutions. For a typicalsample preparation, 0.6 g dry material was dissolved in 2.5 mL DMSO-d₆solvent at room temperature in a glass vial. The DMSO-d₆ solventcontains 0.015 M Cr(acac)₃ as a relaxation agent. The solution was thentransferred to a 10 mm NMR tube for characterization. Quantitativeinverse-gated ¹³C NMR experiments were performed on a Bruker Avance 400MHz (¹H frequency) NMR spectrometer equipped with a 10 mm DUAL C/Hcryoprobe. All experiments were carried out without sample spinning at25.0° C. Calibrated 90° pulse was applied in the inverse-gated pulsesequence. The relaxation delay between consecutive data acquisitions is5*T₁, where T₁ is the longest spin-lattice relaxation time of all nucleiin the measured system. The ¹³C NMR spectra were processed with a linebroadening of 1 Hz, and referenced to 39.5 ppm for the DMSO-d₆ resonancepeak.

Information that can be obtained from ¹³C NMR spectra includes thepercent of hydroxyl conversion, byproduct levels and solid content ofthe reaction product. The carbon next to a hydroxyl group has a chemicalshift change after the carbamylation reaction. The hydroxyl conversionwas calculated from the peak intensity ratio of the carbon after andbefore a carbamylation reaction. In a quantitative ¹³C NMR spectrum,each component of the measured system has a unique resonance peak, andits peak intensity is proportional to the molar concentration of thatspecies. The byproduct levels and solid content were calculated byintegrating the desired peaks. The molar concentration can be convertedto weight percentage if the molecular weights for all species are known.In calculating the solid content, any components other than knownsolvents are classified as solid.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.

We claim:
 1. A process to produce polycarbamate comprising: providingurea in liquid form, wherein the urea is dissolved in water; and addingthe liquid urea to an acrylic polyol in a reactor thereby forming apolycarbamate; wherein the acrylic polyol is dissolved an organicsolvent prior to the step of adding the urea in liquid form to thepolyol; wherein the water and the organic solvent form a heterogeneousazeotrope; and removing the water and returning the organic solvent tothe reactor; and wherein said polycarbamate is characterized by all ofthe followings (i) to (iv): (i) comprising less than 0.2 wt % cyanuricacid based on the total weight of the polycarbamate product; (ii)comprising less than 0.6 wt % biuret based on the total weight of thepolycarbamate product; (iii) comprising less than 2 wt % polyallophanatebased on the total weight of the polycarbamate product; and (iv)exhibiting a Gardner color of less than or equal to
 2. 2. The processaccording to claim 1, wherein the adding the liquid urea to the polyolis conducted in a semi-batch manner.
 3. The process according to claim1, wherein the adding the liquid urea to the polyol is conducted in thepresence of a catalyst.
 4. The process according to claim 1, wherein theremoval of the water is by decantation.